The study of mantle convection is one of the most important topics in geodynamics. Mantle convection causes the transfer of internal heat to the cold parts of the Earth, and the effects of this heat transfer are observed as the motion of tectonic plates on the Earth's surface. Earthquakes, volcanism, and mountain building at the plate margins result from the movement of tectonic plates. Although the mantle occupies a large volume of the Earth, there are many fundamental questions about mantle composition, rheology, dynamics, and history. Many of these questions remain unanswered due to our indirect observations of the mantle. A major tool to study mantle dynamics is numerically analyzing mantle convection equations. In this work, we used Aspect-short for Advanced Solver for Problems in Earth's Convection-code to simulate mantle convection. The geometric model used in the simulation is a box of 4200 km by 3000 km. Using this code, we investigated the effect of different Rayleigh numbers on controlling the mantle convection and creating mantle plumes. Results show that the number of mantle plumes increases with increasing Rayleigh number, and the rising mantle plumes become thinner with the Rayleigh number increasing. Finally, we studied the relationship between the Rayleigh number and the Nusselt number (surface heat flux). We conclude that there is a power-law relation between Rayleigh and Nusselt numbers.

Scattered outcrops of ultramafic - mafic rocks and interbeded sedimentary layers in the North of Fariman - Torbat-e- Jam lineament are exposed mainly at the west of Mashhad, east of Fariman and north of Torbat-e- Jam in Agh- Darband area. Our studies on ultramafic - mafic rocks have revealed several fields and petrographic evidences which demonstrate their volcanic to subvolcanic origin. Moreover, observation of various disequilibrium textures including the presence of glass, elongate and hopper pyroxene and olivine, occurring as pyroxene spinifex and olivine microspinifex textures in mafic and ultramafic rocks, can just be explained on the basis of their volcanic origin. On the basis of geochemical criteria, defined by IUGS for high MgO ultramafic and mafic volcanic rocks, these rocks are classified as komatiitic, picritic and basaltic types. Essential geochemical contrasts, including various ratios of incompatible immobile trace elements and different patterns of REE and spider diagrams, are too high to be explained on the basis of various degrees of partial melting of a uniform mantle source or AFC processes. It is thus possible to consider the role of a heterogeneous mantle source and/or dynamic melting in petrogenesis of these rocks. Furthermore to the cited heterogeneity which can be explained by mantle plume assumption, position of Fariman’s samples in the diagrams of (Nb/Th)N versus (Nb/La)N and Nb/Th versus Zr/Y which mainly plot at the OPB area, and Zr/Y versus Nb/Y which plot on or above DNb line, coincide with the same assumption. Here we have argued that disequilibrium textures had been formed by undercooling of superheated melts, originated from an ascending mantle plume source, and rapid growth of crystals in such a melts. This arguement is favored with regard to high Fo contents of olivines which make necessary equilibrium of these crystals to high MgO contents and hot melts. We have estimated the MgO content and temperature of parent melt as much as 23.74% and 1470-1535ºC respectively based on maximum Fo content of olivine crystal in a komatiitic sample. These values are too high to correspond to a subduction or even a normal MORB related environments; however, similar to a hot spot tectonic setting.

The river plume can be categorized into two general types surface-advected and bottom-trapped and also intermediate type. The river plume classification affects seawater's biological and non-biological characteristics in the river mouth. Given the importance of this issue, using numerical simulations, the plume type of the Arvand river was revealed in this study. The river plume has apparent effects on seawater characteristics of the northwest of the Persian Gulf. For this purpose, the FVCOM model is used for the temperature, salinity, and circulation modelling of the Persian Gulf's water. The model used a horizontal grid of variable triangular elements and a vertical network with 20 Sigma layers. Temperature and salinity at the open boundary were used from the outputs of the HYCOM model. Also, four main tidal components were applied to the model in the open border. After model stability, water column stratification and the shape and width of the river plume were investigated. Several different regional winds were applied to the model to study the wind effect on the plume structure. In no wind, the plume was inclined to the south. The shape and width of the plume change with wind; Thus, the difference between the area of the plume in the two wind modes of 4 meters per second north and south is 300 square kilometres. According to this apparent stratification and the powerful influence of the wind on the plume, the Arvand river has a surface-advected plume that is significant in the fishery, environment, and contamination aspects.

The Siah-Cheshmeh ophiolites at the north-northwest part of the Khoy ophiolites show a dismembered pile of metamorphic units, mantle sequence, and basaltic-andesitic lavas associated with Late Cretaceous pelagic limestones and cherts. The basaltic-andesitic lavas can be divided into alkaline and calc-alkaline varieties. The presence of Ti-rich amphibole prisms and Ti-bearing clinopyroxenes is characteristic of these lavas. The calc-alkaline lavas are characterized by enrichment in LREE and depletion in HFSE while the alkaline lavas display positive LREE and HFSE anomalies. The interaction between mantle plumes with a spreading center can be considered for generation of alkaline basalts while a subduction zone is responsible for the genesis of calc-alkaline basalts.

Boneh shurow metamorphic complex is located in the east of Saghand area, Central Iran. This complex consists of quartz-feldspatic gneiss (mafic minerals< 5%), biotite-amphibole gneisses, metabasics rocks, schists, subordinate dolomitic marble and quartzite interlayers and mafic and felsic magmatic intrusions that they have been retrogressed to lower amphibolite facies. In MORB-normalized plots, the metabasic samples can be classified into two groups: first group does not display Nb-Ta anomaly and second group displays negative Nb-Ta anomaly. Whole rock geochemistry and Sr– Nd isotopic composition of metabasic unites suggest derivation from two different mantlic sources in the back arc setting. A source enriched in Ti, such as plume tail, and an old enriched mantle that has been affected by subduction, can be involved in generation of the first and second group, respectively.

Neogene igneous rocks of the Quchan-Esfarayen magmatic belt (north of Sabzevar) represent post collisional magmatism in the northeast of Iran suture zone. This NW-SE igneous complex occurs as sporadic dome, stock, dyke and lava flow in the belt. The basic lava flows (basalt) and dykes croped out in the Miocene marls around the adakitic domes. The studied rocks include olivine basalt to trachy andesitic basalt in composition with microlitic porphyry, hyallomicrolitic porphyry, glomeroporphyry and flow textures which are composed of olivine, clinopyroxene and plagioclase phenocrysts and microcrysts as main minerals in a glassy or microlitic groundmass. The basalts are sodic in nature, enriched in large ion lithophile elements (LILEs), light rare earth elements (LREEs), high field strenght elements (HFSEs) specially in Nb (20-30 ppm) and depleted in heavy rare earth elements (HREEs). Parental magma of the basaltic rocks originated from 10-15% partial melting from a garnet lherzolitic mantle plume in an intra-arc extensional basin in Miocene time then ascended and extruded in Neogene sedimentary basin via fault and fracture systems. This mantle plume formed by detachment of oceanic slab window and invasion of hot asthenospheric mantle into the mantle wedge over the Sabzevar Neotethyan oceanic subduction zone.